Method for manufacturing sheet-formed buffer material using gelled material

ABSTRACT

A method for manufacturing a sheet-formed buffer material using a gelled material wherein a thermally flexible and weldable covering sheet is applied to each of both surfaces of a flat gel material layer made of gelled material with penetration value of 50 to 200 and a buffer layer is thus made, said buffer layer being divided from above said covering sheet by a dividing means having a thermally welding means whereby said buffer layer is divided by said dividing means to form separate cells and simultaneously said covering sheets of the divided portions are welded by said thermally welding means to form dividing grooves between separate independent cells.

BACKGROUND OF THE INVENTION

The present invention relates to a method for manufacturing asheet-formed buffer material using gelled material, mainly silicone gel.

A gelled material represented by silicone gel can be expected to serveas a buffer material due to its liquid propagation characteristic asdisclosed in the U.S. Patent Application Ser. No. 814726 filed on Dec.30, 1985, now abandoned.

Such silicone gel, however, has a penetration value of approximately 50to 200 which has been measured according to JIS (Japanese IndustrialStandard) K 2530--1976--(50g load) and therefore it has the feature thatthe adhesiveness of the surface is high and the tensile strength and thesurface hardness of this type of gelled material is weak.

To solve this problem, a buffer material using this type of gelledmaterial as a buffer layer is made by covering the whole externalsurface of gelled material with a cloth or, if the gelled material issilicone gel, the buffer material is made by causing a hardened layer tobe formed on its external surface through a chemical reaction.

The conventional buffer material as described above has accompaniedproblems in that the whole single buffer layer is deformed duringabsorption of external shock since the buffer layer made of gelledmaterial is made as single layer and, if this buffer material is usedin, for example, a shoe sole, the whole buffer layer causes transversalslipping and therefore the buffer layer cannot exhibit a satisfactorybuffering performance.

To solve such problems, it is preferable to finely divide the bufferlayer made of a buffer material into a number of separate independentcells so that individual independent cells can independently provide abuffering action and therefore the single buffer layer made of gelledmaterial included in the buffer material need be divided into arrays ofindependent cells.

As such division cannot be realized on the buffer material on which thehardened layer is formed on the surface of gelled material as describedabove, a sewing means such as quilting should be used for a buffermaterial using a cloth as an external covering material as describedabove.

As described above, however, this type of gelled material, particularly,silicone gel with the penetration value of approximately 150, which isthe most desirable material, has a high adhesiveness and, if suchmaterial is handled by the sewing means, silicone gel which adheres tothe sewing needle may lower the processing speed or may be carried awayfrom the external covering sheet to stick to the surface of the externalcovering sheet or neighboring object.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method formanufacturing a sheet-formed buffer material with at least twoindependent cells which contain gelled material with the penetrationvalue of approximately 50 to 200.

This object is achieved by a manufacturing method comprising the stepsof making a buffer layer by applying covering sheets made of a thermallyweldable material to both surfaces of a flat gel material layer made ofgelled material and a process for dividing said buffer layer from abovethe covering sheet, jointing the front and rear covering sheets at thedividing positions and welding the jointed portions by heating.

Another object of the present invention is to provide the method formanufacturing a buffer material whose shock absorbing ability isimproved by overlapping a cushion layer on at least one of said bothfront and rear covering sheets.

This object can be achieved by overlapping a thermally weldable foamedsheet such as polyvinyl chloride, polyurethane or urethane vinyl to theexternal or internal surface of one or both of the covering sheets, anddividing the buffer layer.

Another further object of the present invention is to provide the methodfor manufacturing a buffer material by lamination-forming a thin layerwith excellent heat conductivity such as, for example, aluminum on theexternal surface of at least one of said both front and rear coveringsheets by, for example, a method of vacuum evaporation.

Such buffer material as described above can be used at a location suchas, for example, engine mount and cooler compressor mount where thematerial is subject to thermal effects.

Another further object of the present invention is to provide the methodfor manufacturing a buffer material capable of ensuring division of thebuffer layer by pressing the bottoms of grooves of the buffer layerwhich are formed when the buffer layer is divided.

If the dividing grooves are formed by dividing the buffer layer andseparate independent cells are formed by these dividing grooves, thegelled material which stays at the divided groove portions is extrudedinto independent cell portions and the internal pressure of theindependent cells increases.

If the buffer layer is thick, the welded portions of dividing groovesmay be separated by the increased internal pressure of independentcells. However such separation can be prevented by pressing the dividinggrooves for a while to ensure division of the buffer layer and pressingthe dividing grooves until they are cooled even after welding to fixsolidification of welded portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a part of an example of the buffermaterial manufactured by the method in accordance with the presentinvention,

FIG. 2 is a magnified cross sectional view of a principal part of saidbuffer material,

FIG. 3 is a magnified cross sectional view of a principal part of saidbuffer material in the covering process by the method in accordance withthe present invention,

FIGS. 4A and 4B are respectively an explanatory illustration showinganother embodiment of said covering process,

FIG. 5 is an explanatory illustration showing the dividing methodincluded in the method in accordance with the present invention,

FIG. 6 is an explanatory illustration showing the status of independentcells in said dividing process,

FIGS. 7A to 7C are respectively a bottom view of an example mold for usein the method in accordance with the present invention,

FIGS. 8 to 11 are respectively a perspective view of a part of otherexamples of the buffer material made by the method in accordance withthe present invention,

FIG. 12 is a magnified cross sectional view of a principal part of thebuffer material shown in FIG. 11,

FIG. 13 is a magnified cross sectional view of a principal part showinganother embodiment of said buffer material,

FIGS. 14A to 14D are respectively an explanatory illustration showingthe steps of the processes in another embodiment of the method inaccordance with the present invention, and

FIG. 15 is a cross sectional view showing another embodiment of thepressure-dividing member shown in FIG. 14A.

PREFERRED EMBODIMENT OF THE INVENTION

Referring to FIG. 1, there is shown buffer material 10 obtained by themethod in accordance with the present invention. Buffer material 10 isdivided into a number of independent cells 11 each of which is separatedby the dividing grooves 12. The width of said dividing grooves 12 ispreset in accordance with the purpose of use of buffer material 10; forexample, for a shoe sole, the width of the dividing groove can be set tobe large in case where a large inertia acts in the horizontal directionat the time of sudden stopping motion.

Each independent cell 11 of said buffer material 10 is filled with agelled material as shown in FIG. 2 and finely divided buffer layers 13are thus formed.

Silicone gel with the penetration value of, for example, 50 to 200 isused as this gelled material and Toray Silicone CY 52 (registered tradename of the silicone product of Tray Silicone Kabushiki Kaisha) issuitable as said silicone gel.

The gelled material used for the present invention can be mixed withfine hollow particles such as, for example, Fillite (registeredtrademark) manufactured by Nippon Fillite Kabushiki Kaisha or Expancel(registered trademark) sold by Nippon Fillite Kabushiki Kaisha to reduceits price and specific gravity or with magnetic particles or conductiveparticles to provide magnetic characteristics or electricalcharacteristics.

Silicone gel mixed with fine hollow particles is disclosed in the U.S.Patent Application Ser. No. 814726 cited in "Background of theInvention".

Said independent cells 11 are made as island cells in FIG. 1. However,they can be made to be concentrically multi-annular as shown in FIG. 10or transversally parallel, depending on the case, and the shape ofindependent cells can thus be freely selected. FIG. 3 shows the processfor making said sheet-formed buffer layer 100 of the method inaccordance with the present invention in which the flat sheet-formed gelmaterial layer 100' made of gelled material is covered with coveringsheets 101 and 101' on both its front and rear surfaces.

Production of such sheet-formed buffer layer 100 is disclosed in theU.S. Patent Application Ser. No. 73067 filed on July 13, 1987.

Covering sheets 101 and 101' can serve as the external covering sheetsor at least one of covering sheets 101 and 101' can be providedindependent of external covering sheet 102 as shown in FIGS. 4A and 4B.

If one or both of covering sheets 101 and 101' serve as the externalcovering sheet, covering sheets 101 and 101' are made of a thickerthermally weldable film such as, for example, polyvinyl resin orpolypropyrene resin but, if covering sheet 101 is not used as theexternal covering sheet, a thermally weldable film which is the sheet tobe welded is applied as covering sheet 101 to the inside of an urethanevinyl film or a foamed sheet used as external covering sheet 102 asshown in FIG. 4A or a thermally weldable adhesive agent is applied tothe inside of external covering sheet 102 to form covering sheet 101 asshown in FIG. 4B. In other words, said covering sheet 101 or/andcovering sheet 101' can be formed so that they directly come in contactwith gel material layer 100' and therefore a means for extending thethermally weldable film or a means for applying the thermally weldableadhesive agent can be used.

And also, a thermally weldable cushion layer can be used as coveringsheets 101 and/or 101'. Buffer layer 100 which has been covered in saidcovering process is divided into independent cells 11 by the dividingprocess as shown in FIG. 5.

In this dividing process, the heating press method, high frequencywelding method or ultrasonic welding method are used, and coveringsheets 101 and 101' are adhered through a welding reaction at the sametime buffer layer 100 is divided.

FIG. 5 shows an embodiment according to the heating press method, whereupper mold 21 of molding unit 20 is provided with pressure-dividingmembers 211 which are protruded in the form of the grating and one orboth of upper mold 21 and lower mold 22 are provided with a heatingmeans such as, for example, heater 23.

Said pressure-dividing members 211 serve to divide buffer layer 100between upper and lower molds while being heated by said heater 23 and,at the same time, form weld dividing grooves 12 to make the sheet-formedbuffer material 10 as shown in FIG. 1.

Since there are some problems with this heating press method in coolingdividing grooves 12 and controlling the temperature for heating themold, it is actually preferable to adopt the ultrasonic welding methodand the known means can be used for this method.

In the above discussion the covering process and the dividing processhave been described as separate processes for convenience inexplanation. Actually, in the dividing process, covering sheets 101 and101' can be overlapped onto gel material layer 100'.

In said dividing process, as shown in FIG. 6, bulge 131 as large as anextruded amount of gelled material due to formation of dividing groove12, is formed at the periphery of divided buffer layer 13 insideindependent cell 11 and therefore, for dividing groove 12 with a largercapacity, external covering sheet 102 and covering sheets 101 and 101'need be made of a highly extendable and elastic material.

An example of the mold for use in the method in accordance with thepresent invention is shown in FIGS. 7A and 7C.

Mold 21 shown in FIG. 7A is constructed by providing a number ofprotruded pressure-dividing members 211 in parallel arrangement to formlong rectangular cavities 212 also in parallel arrangement, and thesheet-formed buffer material 10 on which a number of slender independentcells 11 are formed in parallel can be made by using this mold 21.

Mold 21 shown in FIG. 7B is constructed by providing pressure-dividingmembers 211 in a grating pattern to have a number of circular cavities212 and the sheet-formed buffer material 10 with the arrays of separateindependent cells 11 as shown in FIGS. 1, 8 and 9 can be made with thismold.

Mold 21 shown in FIG. 7C has cavities 212 which are concentricallyprovided and pressure-dividing member 211 and normally circular cavity212 is provided at the center of mold 21. The use of this mold 21 allowsmaking of buffer material 10 as shown in FIG. 10.

Though the cavity 212 of said mold 21 shown in FIGS. 7A and 7B is formedto be rectangular in the embodiment, it can be formed to be circular orpolygonal or as otherwise desired and can be made in different sizes.

The size of cavity 212 has an important significance in relation to theheight of independent cell 11.

This is because, when mold 21 depresses buffer layer 100, the gelledmaterial in a part of buffer layer 100 where dividing groove 12 isformed is extruded into independent cell 11 by pressure-dividing member211 and the density of the gelled material inside independent cell 11becomes large.

In this case, if independent cell 11 has large capacity and thepenetration value of gelled material is low, bulge 131 as shown in FIG.6 is formed at independent cell 11 as shown in FIG. 6. If theindependent cell 11 is a square each side of which is, for example, 10mmor less, the independent cell 11 is formed with a bulged top as shown inFIG. 8 and, if each side of independent cell 11 is reduced toapproximately 2 to 5mm, the tops of independent cells 11 are projectedas shown in FIG. 9.

Accordingly, if independent cells 11 as shown in FIG. 9 are provided,high independent cells 11 with an excellent buffering effect can be madewith thin buffer layer 100 and thus the quantity and cost of gelledmaterial to be used for buffer layer 100 which is a component materialcan be reduced.

From this fact, it is known that it is better to provide a number ofsmall-diameter cavities 212 in a high density on mold 21 and thus toincrease the quantity of gelled material to be stored in independentcell 11 in reference to the capacity of independent cell 11 when formingdividing grooves 12 for obtaining a substantially thick sheet-formedbuffer material.

Since the bulging height of independent cell 11 can thus be varied inaccordance with its size, buffer material 10 on which independent cell11 at the center are made to be low and independent cells 11' at theperiphery are made to be high, for example, as shown in FIGS. 11 and 12can be made and it can be used in sports goods such as knee supporter.In this case, the number and width of dividing grooves 12 can bedesigned so that buffer material 10 can easily be bent along the contourof a human body which will wear it.

In the method in accordance with the present invention, aftersheet-formed buffer material 10 has been made by dividing buffer layer100, thin film layer 30 with rust preventiveness and thermalconductivity can be applied to this buffer material 10 by a means suchas, for example, vacuum evaporation, ion plating, sputtering,non-electrolytic plating and metallic flame coating.

FIG. 13 shows the buffer material 10 onto which aluminum isevaporation-deposited as said thin film layer 30 and this buffermaterial 10 can use independent cells 11 as radiating members.

In case of dividing buffer layer 100 shown in FIG. 5 into independentcells 11 each of which has a relatively large area by the method inaccordance with the present invention described above, an excessiveincrease of the internal pressure of independent cell 11 due toacceptance of gelled material owing to formation of dividing groove 12is avoided since the quantity of gelled material which is forced intoindependent cells 11 along with formation of dividing groove 12 isrelatively small compared with the capacity of independent cell 11. Alsoin this case, if the penetration value of gelled material is small,bulge 131 is formed at the periphery of independent cell 11 as shown inFIG. 6 and therefore the gelled material will not be concentrated at thecentral portion of independent cell 11. However, if the area ofindependent cell 11 to be formed on buffer layer 100 is less than 1 cm²,the quantity of gelled material which is forced into independent cell 11along with formation of dividing groove 12 increases compared with thecapacity of independent cell 11 whereby a problem is expected in thatthe thermally welded portions of both covering sheets 101 and 101' areoften exfoliated due to the increased internal pressure of independentcell 11.

Such sheet-formed buffer material provided with small independent cells11 can find a number of practical applications since its bufferingeffect can be improved by bulging independent cells 11 so as to have alarge height as shown in FIG. 9 and the quantity of gelled material tobe used can be reduced by increasing the area of dividing groove 12 tothe whole buffer material 10.

The processes as shown in FIGS. 14A to 14D are advantageous forprovision of such independent cells 11 with large expandability.

Buffer layer 100 to be produced by the method of this embodiment isassumed in case that the quantity of gelled material to be forced intoindependent cells 11 by formation of dividing grooves 12 is large inreference to the capacity of independent cells 11, including the casethat the thickness of buffer layer 100 is large, and it is not alwayslimited to the case that the width of dividing groove 12 is large.

In this embodiment, heating type dividing member 213 is assembled withdepressing members 214 and 214' at its both sides and these 1-inch widedepressing members 214 and 214' are set to be depressed against bufferlayer 100 before dividing member 213 so that covering sheets 101 and101' are joined as shown in FIG. 14A.

After the grooves thus have been forcibly formed at the expectedportions of the dividing grooves on buffer layer 100, dividing member213 comes into the cavities as shown in FIG. 14B and the joined portionsof covering sheets 101 and 101' are welded by, for example, highfrequency heating.

Dividing member 213 rises to return to the home position as shown inFIG. 14C before said depressing members 214 and 214', and subsequently,depressing members 214 and 214' rise to return to the home positionsalong with rising motion of mold 21 as shown in FIG. 13D after thewelded bottom of dividing groove 12 has fully been cooled.

In this embodiment, recessions are formed in advance by said depressingmembers 214 and 214' at the parts where provision of the dividinggrooves is expected and the gelled material is transferred intoindependent cells 11 due to formation of the recessions by thedepressing force of depressing members 214 and 214'.

Said dividing member 213 is forced into the recessions formed by saiddepressing members 214 and 214' and the shape of which is maintained andthe bottom of the recessions is thermally welded by dividing member 213.The bottoms of recessions are firmly held by depressing members 214 and214' at this time of welding the force which acts to exfoliate coveringsheets 101 and 101' along with the increase of the internal pressure ofindependent cells 11 will not be applied to the bottoms of recessionswhich will form the bottom of dividing groove 12. Accordingly, thecovering layers are positively heated and welded by dividing member 213.The bottom of said dividing groove 12, that is, the bottom of saidrecession is released from said depressing members 214 and 214' after ithas fully been cooled or completely welding-adhered and therefore thecovering sheets 101 and 101' will not be exfoliated even though theforce due to the increase of internal pressure of independent cells 11is applied to the bottom of groove 12.

In the embodiment, said depressing members 214 and 214' are providedwith differential means such as, for example, springs 215 and 215' toobtain a differential motion for dividing member 213, and depressingmembers 214 and 214' are designed so that they move prior to dividingmember 213 when mold 21 is lowered and move after dividing member 213when mold 21 is raised.

Said depressing members 214 and 214' can be constructed so that a strongforce acts on the corners of the recession by dividing the inside partsof the extreme ends of depressing members 214 and 214' as shown in FIG.15.

In said embodiment, the construction of the mold for which dividingmember 213 is provided with depressing members 214 and 214' is shown. Asimilar effect to the above can be achieved by controlling the heatingmotion of dividing member 213 without using the depressing members. Inother words, after dividing member 213 has been fully pushed into bufferlayer 100 and said buffer layer 100 has been fully divided, dividingmember 213 can be heated to welding-adhere covering sheets 101 and 101',then the welding-adhered bottom of dividing groove 12 can be cooled bycooling dividing member 213 which remains as is and dividing member 213can be raised to return to the home position after cooling.

Said mold 21 is preferably provided with a dividing edge at itsperiphery to carry out trimming of the welded peripheral edges ofcovering sheets of buffer layer 100 when the buffer layer is to bedivided. Thus, the periphery of the sheet-formed buffer material whichis a product can be shaped at the same time as forming.

The present invention is not limited to the embodiments described aboveand available in various variations within the range which does notdeviate from the claims and the spirit of the present invention.

What is claimed is:
 1. A method for manufacturing a shock absorbingsheet material comprising silicone gel, comprising the steps of:a.forming an assembly comprising a flat sheet-shaped gel layer made ofsilicone gel with a penetration value of about 50 to 200, having on eachside thereof a flexible covering film having thermal weldability atleast on the side which faces said gel layer, b. depressing saidassembly from the outside of at least one of said covering films by adividing means including a heating means therefor, to divide said gelmaterial layer by pushing the gel material layer laterally away from thedividing means, while forcing at least a portion of said covering filmson either side of said gel material layer to directly contact eachother, thereby simultaneously forming at least two independent cellswhich are thus divided and substantially swelled by pushing saidsilicone gel material therein, c. heating said portions where said upperand lower covering films directly contact each other by said dividingmeans which is heated by said heating means to weld the internalsurfaces of said covering films to form a line of dividing grooves whichdefine said cells, and d. releasing and removing the resultant shockabsorbing sheet material in which said dividing grooves are formed, fromthe dividing means after said heating and welding.
 2. The method inaccordance with claim 1, wherein said dividing means forms island typeindependent cells in said sheet material.
 3. The method in accordancewith claim 2, wherein said dividing means forms island type independentcells having diameters of approximately 2mm to 10mm on said bufferlayer.
 4. The method in accordance with claim 2, wherein said dividingmeans forms at least two kinds of island type independent cells havingdifferent areas on said sheet material.
 5. The method in accordance withclaim 1, wherein said dividing means forms striped independent cells onsaid sheet material.
 6. The method in accordance with claim 1, whereinsaid dividing means forms concentrically annular independent cells onsaid sheet material.
 7. The method in accordance with claim 1, whereinsaid covering sheet film has a non-thermally weldable external coveringlayer on its external surface.
 8. The method in accordance with claim 1,wherein said covering film has a thin metallic film on the outer surfacethereof.
 9. The method in accordance with claim 8, wherein said thinfilm metallic is formed after said shock absorbing sheet material hasbeen removed from said dividing means.
 10. The method in accordance withclaim 7, wherein said covering film is a cushion layer.
 11. The methodin accordance with claim 7, wherein said covering film has a thermallyweldable adhesive agent applied to the internal surface thereof.
 12. Themethod in accordance with claim 1, wherein said gelled material containshollow particles.
 13. The method in accordance with claim 1, whereinsaid gelled material contains magnetic particles.
 14. The method inaccordance with claim 1, wherein said gelled material containsconductive fine particles.
 15. The method in accordance with claim 1,wherein the heating of said dividing means is stopped after it dividesand welds said covering sheet and keeps depressing the bottom of saiddividing groove until said dividing groove is appropriately cooled. 16.The method in accordance with claim 1, wherein said dividing means isprovided with a pair of depressing members which divide said shockabsorbing sheet material, said depressing members being provided withinterval spaces, and a dividing member which is located between a pairof depressing members, said dividing member being heated by the heatingmeans, said dividing member coming into a recession formed by dividingsaid buffer layer with said depressing members and separating from therecession after the bottom of said recession has been heated and adheredby welding, and then releasing said depressing member from said sheetmaterial after the bottom of said recession has been cooled.
 17. Themethod in accordance with claim 16, wherein the insides of the extremeends of said depression members are chipped.
 18. The method inaccordance with claim 1, wherein at least one of said covering sheetswhich are respectively applied to both surfaces of said gel materiallayer is made of an expandable film.
 19. The method in accordance withclaim 18, wherein said covering sheet is made of an elastic film.